Police in the Former Yugoslav Republic of Macedonia on Saturday fired tear gas and stun grenades at migrants and refugees stranded for days on its southern border with Greece, as they try to make their way to western Europe.

Tensions reached boiling point as Macedonian security forces began erecting a metal fence along the frontier.

As Europe’s worst migrant crisis since World War Two continues, the Macedonian government says it won’t seal off access to refugees fleeing war.

A government spokesman said the aim of the fence was “to direct the inflow of people towards the controlled points for their registration and humane treatment.”

“We would like to underline that the border will remain open,” said spokesman Aleksandar Gjorgjiev.

“We will allow passage for the people who come from war-affected regions as we have done thus far.”

But along with other countries, Macedonian authorities are now turning back other migrants, leading to a chaotic build-up at the Macedonian-Greek